This work is designed to elucidate some of the factors which regulate removal of neutral lipid from the circulation. Triglyceride transport from the circulation to adipose tissue is known to depend upon hydrolysis of lipoprotein bound triglyceride by lipoprotein lipase. Lipoprotein lipase, in turn, appears to be regulated by a factor in serum. We have shown that this factor enhances lipoprotein lipase release from fat cells in vitro. We propose to isolate lipoprotein lipase from human heart and adipose tissue and to characterize the purified preparations using appropriate chemical, physico-chemical and immunologic procedures. We also plan to develop immunoassays for lipoprotein lipase and for lipoprotein lipase releasing factor of serum. Such assays will allow us to measure precursor, inactive, and defective proteins, as well as active forms. Antisera will also be used to localize lipoprotein lipase and lipoprotein lipase releasing factor in cells and tissue at the light and electron microscopic levels. We plan to study the role of lipoprotein lipase and the lipoprotein lipase releasing factor in lipid transport. This will be done by determining the effects of nutritional, hormonal, and altered metabolic states on their activities. These activities will be correlated with plasma triglyceride concentrations especially in hyperlipemic subjects. We will determine whether changes in adipocytes occur as a consequence of exposure of these cells to lipoprotein lipase releasing factor. Methods already employed successfully in studying lipoprotein lipase from animal tissues and methods already used for isolation and immuno-chemical characterization of lipoproteins will be used.